The invention disclosed herein relates to a method for the synthesis of lithium based mixed oxides, from their elementary oxides, by subjecting them to a high energy milling process, that is a mechano-chemical synthesis creating the lithium based mixed oxides.
Lithium based mixed oxides of the formula Li Mxe2x80x2xxe2x80x2Mxe2x80x3xxe2x80x3 . . . Oy have recently found many uses. These oxides are mainly used in the field of rechargeable lithium batteries and, additionally, may be used as cathode materials.
Conventional methods of synthesis of lithium based mixed oxides of the formula LiMxe2x80x2xxe2x80x2Mxe2x80x3xxe2x80x3 . . . Oy are usually based on chemical synthetic methods of solutions, precipitations, gels, etc. Even more commonly, these methods of the synthesis of lithium based mixed oxides are based on synthetic methods of the ceramic type, in which the base materials are intimately mixed in the required proportions and heated for solid state reactions and sintered for a requisite period of time at a high temperature, usually in the range of one thousand degrees Celsius. This, of course, requires very specialized equipment and conditions, and the extremely high-energy heat inputs associated with the conventional synthesis of the lithium based mixed oxides.
Accordingly, there is presently a need for a low heat energy input process for the synthesis of lithium based mixed oxides, which is simple, economical, and operable at room temperature conditions.
Therefore, a feature of the present invention is to assist in providing a process to create a lithium based mixed oxide at room temperature without requiring the addition of substantial external heating.
Another feature of the present invention is to assist in providing a process to create a lithium based mixed oxide utilizing high energy milling.
Another feature of the present invention is to provide an economic process for creating a lithium based mixed oxide.
Yet another feature of the present invention is to assist in providing a process to create a lithium based mixed oxide with multiple base metals other than lithium.
Still yet another feature of the present invention is to assist in providing a process to create a lithium based mixed oxide wherein one of the multiple base metals, other than lithium, is received, or incorporated, from the material of the crucible utilized in the high energy milling process.
The present invention relates to the synthesis of lithium based mixed oxides of the above formula from their elementary oxides by subjecting them, for a certain period of time and at room temperature, to a high energy milling process, or mechano-synthesis. By such method, it is possible to obtain composite oxides having crystallites of nanometer dimensions, that being approximately 100 nanometers or less in dimension, by way of a true chemical synthesis without addition of heating, as occurs in conventional synthesis methods.
The present invention is a process for the production of a lithium based mixed oxides of formula (LiMxe2x80x2xxe2x80x2 . . . Oy) which may be conducted at room temperature, in a process which is simple, economical, and requires no prior heating to obtain the starting mixed oxide structure. A lithium oxide and a second and subsequent oxide having a base metal element (Mxe2x80x2) as well as the additional metal elements of (Mxe2x80x3, Mxe2x80x2xe2x80x3 . . . ) present, are combined at room temperature using a high energy milling process applied at a controlled atmosphere and without substantially extraneous heat added to the synthesis. The milling is performed until the synthesis produces a lithium based mixed oxide having crystallites of nanometer dimension. It is preferable to have a controlled atmosphere wherein oxygen availability is controlled. This can be accomplished by using an argon gas atmosphere.
Preferably, the metal based elements are selected from the group comprising Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al and Mg. The lithium based mixed oxide can be of the formula (LiMxe2x80x2xxe2x80x2Mxe2x80x3xxe2x80x3 . . . Oy), where the lithium oxide has at least one base metal other than lithium. One of these base metals can be partially or completely received, or incorporated, from the crucible utilized for the high energy milling process. As well, the synthesis xxe2x80x2, xxe2x80x3 and so on and y represent the atomic fraction of the metals in the mixed oxide and of the oxygen respectively. It is also preferable that one of the base elements, of either of the above equations, is cobalt.
An alternative aspect of the present invention is providing a method of manufacturing a lithium based mixed oxide having the steps of combining a lithium based powder and a second base metal oxide powder. These combined powders are then high energy milled. This milling is a controlled milling having a substantially controlled atmosphere, without the addition of substantial extraneous heat, and is performed until the lithium based mixed oxide has crystallites of substantially nanometer dimension. An atmosphere of argon gas may be used as the controlled atmosphere. It is preferred for the second and subsequent base metal oxide powder to have an element selected from the group of: Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al and Mg. Preferably, the milling is performed for at least 20 hours in a tungsten carbide crucible under an argon atmosphere. It may also be preferable to combine a third base metal oxide to the lithium based mixed oxide, and it may be preferable for that third base metal oxide to be received from the crucible utilized for the high energy milling.
The invention however, is not limited to the above-referenced metals and may include other metal elements suitable for the synthesis of lithium based mixed oxides as may be found in the groups of the periodic table, include in group of IA to IIIB.